Total knee arthroplasty fibrosis following arthroscopic intervention

Although arthroscopy is generally considered to be a relatively benign procedure with limited trauma to periarticular soft tissues, post-arthroscopic bleeding as well as osmolality differences between the normal saline used to irrigate and the native synovial fluid (282 vs. 420 mOs) can lead to capsular reactions. Therefore, the purpose of this study was to evaluate whether capsular reaction occurred after knee arthroscopy, by comparing a matched cohort of patients who either did or did not undergo prior arthroscopic surgery. Specifically, we compared histological features such as: (I) synovial thickness; (II) cellularity; and (III) the amount of fibrous tissue for each cohort.

Prior to their total knee arthroplasty (TKA), 40 consecutive patients who had previously undergone arthroscopy were matched to 40 consecutive patients who had not. During each patient's TKA, a biopsy of the capsule and fat pad was taken and formalin sections were sent to pathology to assess for synovial thickness, cellularity, and the amount of fibrous tissue. The pathologist was blinded to the groupings. Findings for all histologic features were classified as equivocal, slight to moderate, and moderate to severe.

There were a significantly higher proportion of patients who had increased synovial thickness in the prior arthroscopy group as compared to the no-prior arthroscopy group (97.5% vs. 0%, P<0.001). Additionally, there were a significantly higher proportion of patients who had increased cellularity in the prior arthroscopy group as compared to the no-prior arthroscopy group (60.0% vs. 0%, P<0.001). There were also a significantly higher proportion of patients who had increased fibrous tissue in the prior arthroscopy group as compared to the no-prior arthroscopy group (95% vs. 62.5%, P<0.001).

Arthroscopic surgery may have long-term effects on capsular tissue as surgical observations of patients with prior arthroscopic surgery from this study found that the capsule is thicker and denser. Histologic assessment confirms there may be increased synovial thickness, increased cellularity, as well as thickening of fibrous tissue. This preliminary study and further evaluation are required. This suggests that arthroscopic surgery may have long-lasting effects on periarticular tissue especially the capsular tissue which may have implications for pain and functional recovery.